Method of determining nickel content of steel



Patented Oct. 26, 1948 METHOD F DETERMlN-ING NICKEL CONTENT OFSTEEL Frederick B. Clardy, Portsmouth, Va.

No Drawing. Application: September 16, 1946, Serial No. 697,167

Claims: (Cl. 23-230 (Granted under the act of" March 3, 1883; as amended April 30, 1928; 370 0. G. 757) a This application is a continuation-in-part of application: Serial No. 601,292, filedby. this inventor, Frederick B. Glardy; on. June 23;, 1.94:5,v for Method of andmaterials for determining. nickel content of steel; now abandoned.

This-inventor has found that, Whilethe process and material used as defined in his applicati'on, Serial No. 601,292 produced a nickel precipitate, the intensity of the red color of'which is proportional to thequantity of' nickel present in the alloy, the color so liberted; is not permanent. It fades and. determinations of the percentage of nickel present basedupon relatively old stains are likely to be. erroneous;

So much of application 601,292 as. covers v the basic process. and the same reaction components as usedin this present application are adopted herein.

Therefore, this. invention. relates to an improved nickel spot testmaterial and its method of preparation and use.

More particularly, this invention is directed to a method of testing for nickel" content in steel and other metal alloys which is non-hazardous. It involvesthe use of only a weak acid solution and especially preparedabsorbent test sheets. The test can be performed by an inexperienced operator and is. reliable. According to-these improvements, any metal which. has beendissolved. and whosepH is approximately 7; such as from 6-8, will give a positive test for nickel if nickel is-present above 0.l.0%-or 020%.

Prior to thisinvention, spot tests for the presence of'nickel' were used. throughout the industry to. identify nickel bearing alloys: to determine the type of alloy. It is exceedinglyv important that a convenienttest beavailable. as: it is estimated, forexample, that. 75% of the-steel alloys in use today contain nickel in varying amounts. Theprior. spot tests were usuallyv made with theaid The I have found that all of thedisadvantja es and:

diificulties can be overcome by effecting solution of the alloy metals as by a dilute acid solution and absorbing the reaction products on my specially developed filter paper or other absorbent materials which have been. treated with; four chem-- ical compounds (1)- to decolorize the: basic metal salt, (2) to buffer thev excess acid; (3:) to fixanch render permanentthe. color of the precipitate-and; l) dimethylglyoxime to react with the nickel: to give its characteristic red action.

Any salt which will form colorless iron salt as for example, the alkali. metal; phosphates: and. fluorides; may be used as a. decolorizing material for low alloy ferrous;- metals (steel) in which. iron is, of course, the, basicmetal. Suitable-- buffers include sodium acetate. ammonium ace-- tate, potassium acetate; The mostefiicient color fixing component has. been found to. be sodium: pyrophosphate.

Thus the preparation of the. various reagents comprises impregnating the filter paper with sodium pyrophosphate, sodiumfluorida sodium ace-- tate, and dimethylgloxime. Also... the acid solu-' tion is prepared by adding sodium phosphate; so-- dium pyrophosphate to 10% solution of: nitric. acid. In creasing amounts of. phosphate; pyro. or ortho, tend to diminish the-color of the'nickel precipitate. Decreasing, the amounts of these. two ions increases the brown color-due to-iron hydroxide.

The treated paper readily gives apositive clear red. color in the presence of 0.0% nickel; a faint. redcolor in the presence of. less than 0.5% nickel, and an increasing amount. of, color for-percentage above 0.5%.

It is therefore an. objectof the. invention: to; provide a method. of spot testing for nickelcone tent of alloys. by the useof, a dilute acidsolution. and. test sheets.

Another object is to provide atest filter. paper:- or other absorbentmaterial treated witha. decob orizing agent, a bufier, a color fixing agent, and, an alcoholic solution of. dimethylglyoxime.

Another object isto provide a test filter paper treated with asalt thatwill. form substantiallycolorless iron salts with low alloy ferrousmetal; in acid solution, a small quantity of pI-I control substance and dimethylgl'yoxime.

These and other objects of invention will be manifest fromthe description. and claims.

According. to. a. preferred embodiment, sheets ofjfilter paper 18. by. 22.v inches are soaked'in a= solution containing 10. parts C. P. sodiumwacea tate (NaC2H3O2.3H2O), 3 parts. of sodium fluoride, (NaF), 5 partsof- C: P: sodium pyrophosphate (NaiPzov-lofizol and epartsoft distilled; water; The;- paper, is driedfiat: and thenisoakedx in a, 1% alcoholic: solution. of! dimethyl'glyoaime. The: paper is. again. dried: and. out iizito. strips 0 1" circles as desired. The acidi solution: is madeby dissolving 13 grams of sodium phosphate (Naa) PO4.10H2O), 1 gram of sodium pyrophosphate (N8.4P2O7.10H2O) is distilled water, adding 10 ml. of concentrated nitric acid (e. g. 1.42)

and diluting to 100 'ml. with distilled water. In general, the phosphates are preferred because they are'inexpensive and non-hazardous.

When low alloy ferrous steels, for example, are to be tested for nickel content, all that is required is to smear a drop (0.05 ml.) of the acid 2. A dried absorbent sheet material for use in determining the nickel content of ferrous alloys in acid solution, consisting of a sheet of absorbent material impregnated with an aque-- ous solution consisting of 10 parts sodium acetate (NaCzHsOzBI-IzO), 3 parts of sodium fluosolution over an area the size of a dime of the 6-8, a red color precipitate is formed. Accord-.

ing to these improvements, this proper pH is obtained by permitting the acid to react to completion or by buffering the excess acid as above described.

In plant work, samples of steel filings, millings, or turnings are identified by first using nitric acid in the test so that the reaction subsides at about a pH of 7 and forms a slight brownish precipitate of ferric hydroxide. The ferric hydroxide may be dissolved in a weak acetic solution. The test in such cases will be as follows with the results similar to the above.

Approximately gram of the metal is put into a 25 ml. beaker, to which is added ml. of 1:1 nitric acid (accurately measured from a ml. burette calibrated to ml. division). When the action has subsided, 5 ml. of a 3% acetic acid is added, the solution stirred and the paper is then quickly dipped into the solution, removed and placed on a white surface, pressed free of excess solution with a, blotter, and the color of the same compared with a set of standard stains. The total time required for the test is less than 30 seconds. In foundry control work, the nickel content of medium steel is usually under 0.50% which is easily determined as above. When the nickel content exceeds this figure it is redetermined colorimetrically.

The advantages of the process are that no prior training or instruction is necessary. The method is very reliable and will indicate the presence of nickel as low as 0.3%. No strong acids or bases are used and the acid solution is nonhazardous and safe. Only one solution is used which eliminates possible errors from the use of several solutions which could become dislabeled and used in incorrect order.

The invention described herein may be manuto form colorless salts of the basic metal of the alloy, an alkali metal acetate buffer to maintain the solution at a substantially neutral pH value, and an alcoholic solution of dimethylglyoxime to precipitate the nickel.

ride (NaF), 5 parts of C. P. sodium pyrophos- 'phat'e (Na4P2Om10I-I2O), and 80 parts of distilled water, the said sheet dried after impregnation with this solution and then saturated with a one percent alcoholic solution of dimethylglyoxime.

3. A dried absorbent sheet material for use in determining the nickel content of ferrous alloys in acid solution by absorption of said solution consisting of a sheet of absorbent paper impregnated with an aqueous solution consisting of 10 parts sodium acetate (NaCzHaOaBHzO) for buffering said solution of alloy to a substantially constant neutra1 pH value, 3 parts soduim fluoride (NaF) to form a substantially colorless salt with the iron of the alloy, 5 parts C. P. sodium pyrophosphate (NmPzOmlOI-IzO) to fix and render permanent the color of the nickel precipitate and parts of distilled Water, the said sheet dried after impregnation with said acqueous solution and. then saturated with a one percent alcoholic solution of dimethylglyoxime for precipitating the nickel as a red crystalline precipitate.

4. An acid solution for dissolving ferrous alloys consisting of a solution of mixture of 13 grams of sodium phosphate (NazPOnlOHzO), 1 gram of sodium pyrophosphate (NzuPzOmlOHzO) in water, 10 m1. of concentrated nitric acid (S. G. 1.42), the solution diluted to a volume of ml.

5. In a process of the colorimetric determination of the nickel content of ferrous alloys, the steps consisting of applying a small quantity of a dilute solution of nitric acid, sodium phosphate, and sodium pyrophosphate to the cleaned surface of a piece of the alloy and absorbing the resultant solution with a dried absorbent material impregnated with an aqueous solution of an alkali metal acetate for buffering the solution of the alloy to a substantially neutral pH value, a salt selected from the class consisting of sodium acid phosphate and an alkali metal fluoride for forming colorless salts with the iron of the alloy, an alkali metal pyrophosphate for fixing and rendering permanent the color of the nickel precipitate and an alcoholic solution of dimethylglyoxime for precipitation of the nickel in the alloy, whereby a red colored precipitate of nickelic dimethylglyoxime is formed, the intensity of the color of which is proportional to to the amount of nickel present and is fixed and permanent in color.

FREDERICK B. CLARDY.

REFERENCES CITED The following references are of record in the file of this patent:

Williams, J. Ind. and Eng. Chem., Anal. ed., 14, pp. '72 and '73 (1942).

Murray et al. J. Ind. and Eng. Chem., Anal. ed., 10, pp 1-5 (1938). 

